I need to buy a crate (I will be getting a sturdy wire crate) but I'm not sure if I should go with the 42" or the 48"? If it helps, I will be getting a female and her mom is around 80 pounds and dad is around 90-100 pounds.
If you have the space and money then I would buy the 48. This way she can spread out more inside it when she is an adult. However I have a 42 inch one and that is big enough for my 75 pound female, she just cant stretch out. So if I were to do it again I would buy the biggest.
Frag is an 80lb male, and can fit into a 36" for a few hours if need be for travel. He has a 48" at home that he snoozes in and is comfortable in, but at night he only uses about half of it (because it's wider) so he curls up in the back. I honestly think he'd be just fine in a 42", and if you're getting a female that should be smaller anyway, I would go with a 42".
I have a 42" for Jamie at the time no stores around me carried the 48". She hopefully won't get as big as Victor or I will have to upgrade her. Victor can fit into Jamie's crate but he is so tall that his ears stick out of the top. The Tractor Supply near me finally got a 48" so I got that size for Victor he loves it and has plenty of room. He can stand up/sit comfortably and no ears sticking out of the top.
Shasta is 70 pounds and about 24.5 inches at the shoulder at 7 months old. Her mom was 80 pounds and her dad 115. She can still fit into the 42" crate but she can barely turn around. Even so, she doesn't balk at going in, but we only use it now occasionally.
I have a 42" for my dog. He is male and 77lbs. He doesn't really stand it it, but when he sits his ears get scrunched. He doesn't seem to have an issue, as he uses it mostly for sleeping. He seems to be able to stretch out decently in it.